Port workers in Brisbane and Sydney are defying orders from Australian authorities on Tuesday to end their protests against the late night sacking of employees via SMS and email, and immediately return to work.

Hundreds of workers are gathering for a fifth straight day at facilities run by Hutchison Ports Australia (HPA), following Thursday night's SMS and email message informing 97 of its 224 dock workers that their employment had ended.

HPA has previously said the job cuts are part of a move to downsize and due to financial losses but the Maritime Union of Australia (MUA) claims the company wants to replace workers with machines.

Australia's Fair Work Commission held a hearing into the sackings in Sydney late Monday night, with Deputy President Anna Booth ordering an end to the picketing.

However a MUA spokesman told local reporters picketing would continue.

MUA national secretary Paddy Crumlin however said the union was not responsible for the picket and is not at liberty to stop it.

Workers at Sydney's Port Botany voted on Tuesday morning not to return to work, saying they would "stick together" in support of their sacked colleagues.

Port workers in Brisbane have been told to make their own decision regarding the commission's orders, however Bob Carnegie from the union's Queensland branch vowed protest action would continue after the picket line on Monday stopped truck deliveries to one of HPA's births.

"We will stay for how long it takes - if it takes one more day fantastic, if it takes one more week okay, if it takes one more year that's fine too," Carnegie told Australia's national broadcaster on Tuesday.

"We will stay the length that's required to bring justice to workers who have been wronged."

Local media reported HPA cut power to the Brisbane picket line on Monday morning, however at least 29 different unions supporting the protesters provided food, tents, generators and portable toilets.

The matter is set to return to the commission on Friday.